PREDICTION
I predict that if the length increases then the resistance will also increase. I think this because the longer the wire is, the more atoms there will be and so the more likely the electrons are going to collide with the atoms. This tells me that if the length is doubled the resistance should also double. This is because the length is doubled the number of atoms will also double. My graph should show that the length is proportional to the resistance. I think that my graph might show me that as the length of the wire increases, so will the resistance. I also believe that my graph will show a positive correlation. I believe that I have a good range of measurements, and hope that these will give me some reliable results.
PLAN
Equipment:
- Power Supply – Power Pack
- Ammeter
- Voltmeter
- 140cm Constantine wire 30 SWG
- Meter Ruler
- Crocodile Clips x4
- Connecting Wires x5
I have chosen to use Constantine wire as from my pelimenry results told me that it does not have a small resistance like copper, and it also had the highest resistance, which should make it easier to measure.
I have also chosen to use 7 different points to measure, to give me a good range of results. I will also do the experiment 3 times to make my results more accurate. The lengths that I have chosen are:
140cm – 120cm – 100cm – 80cm – 60cm – 40cm – 20cm
This is what my experiment will look like:
Key variable
This will be the length of wire, the main aim of this investigation is to see, whether the length of a wire should or will affect the resistance on it. Hopefully we will be able to see if my prediction is right. In theory it should be right, as in reality, if a person walks for a long time, they will become tired and will not be a strong as they did when they first started.
Method
- COLLECT EQUIPMENT THAT IS NAMED IN EQUIPMENT LIST
- CONNECT CIRCUIT SO IT LOOKS LIKE THIS:
- I WILL THEN MAKE SURE ALL MY COMPONENTS ARE WORKING PROPERLY.
- NEXT I WILL THEN MAKE SURE THAT THE DISTANCE BETWEEN A AND B IS MEASURED BY A METRE RULER TO MAKE SURE IT IS THE RIGHT LENGTH, AND IS THE LEGTH SPECIFIED IN THE TABLE BELOW:
- THEN I WILL RECORD THE READING ON THE AMMETER AND VOLTMETER ONCE THE TWO START TO SHOW A READING.
- ONCE I HAVE TAKEN ALL THE RESULTS FOR THE TABLE, I WILL WORK OUT THE RESISTANCE FOR EACH OF THE READINGS USING THE FORMULA: R= V/I
- I WILL THEN REPEAT THE EXPERIMENT ANOTHER TWO TIMES TO GIVE ME MORE ACCURATE RESULTS.
Fair test
To make sure that this is a fair test, I will make sure that the when the power supply is on, that none of the wire is touching another part. I will also keep the same piece of wire thorough out the investigation. Also I will use a ruler to check that the piece if wire is the correct length.
Safety
I will not touch the wire will the circuit is on and will not touch it for a few seconds after.
Results
Experiment 1
Experiment 2
Experiment 3
Table Showing Averages
From the tables, I can see that as the length of the wire increases, so does the resistance. This is what I predicted and can see from my averages table that as current increases, the voltages declines
From my graphs I can see that the longer the piece of wire is, the higher the resistance becomes. So therefore the shorter the piece of wire is, the less the resistance is. This proves that my prediction was right and that the length of a wire does affect the resistance. In my case, the difference was about 7 ohms from 20 cm to 140cm.
Conclusion
I think that from my results, I can see that my prediction was right. The resistance did change in proportion to the length. This is because as the length of the wire increased, the electrons that made up the current, had to go though more fixed particles through the wire. As the length of the Constantine wire increased, so did the voltage, whilst the current declined. My graphs show me a positive correlation, which tells me that as the length of the wire increases so does the resistance.
Evaluation
Overall, I think that my results were reliable, one reason is that I did the experiment three times. From my graph I can also see that I had one anomaly result, but I believe that it has not affected the overall experiment. I am also glad that I chose Constantine wire as it gave me a good range of results unlike copper, which would have given me poor results.
I also saw that I did get some odd results but that may be due to a mis-hap during the experiment, like loose connections or faulty components.
From this I can also see that this wire would not be suitable for using in power lines as it shows it is not as good as copper at conducting electricity. I am happy with the range from A to B I chose as it gave me a good range of results. On average there was a 7-ohm difference between 20cm and 140cm. Changes I could have made to give my results more reliable is to use a larger range, like 200cm. Or use a maybe use the same pieces of equipment the whole way through.
